In mechanical drive systems in which the system is subjected to particularly heavy loads or where it is extremely important that the load be safely handled, it is critical that rotating members which are connected together have a highly secure and safe connection arrangement. A further requirement of such mechanical drive systems is that the connector means between the rotating members be readily installable and removable without the need for disassembly of other components of the system or mechanical stress on such components. An example of a mechanical drive system in which both of these requirements are desirable is a hoist system having a rotatable member such as a drum for lifting and lowering loads. The hoist may have a permanent stationary location or it may be movable, for example the hoist may be mounted on a crane for movement with the crane to various locations for lifting and carrying objects. Drive gear mechanisms such as reduction gearboxes which are specifically designed for the operation of a device such as a hoist include a highly secure connection to the hoist. However, such custom designed drive gear mechanisms are expensive and their installation with the hoist on a supporting framework is typically time consuming and costly. Further, if it is necessary to remove the hoist or drive gear for repair, it may be necessary to partially disassemble the drive gear mechanism to permit its removal or the removal of the hoist. This disassembly work is also time consuming and expensive. A solution to the high cost of a custom drive gear mechanism and its time consuming problems of installation and removal, is to use a standard drive gear mechanism with a standard connector for connecting the drive shaft of the drive gear to the driven apparatus. Standard connectors typically will permit a relatively easy connection and removal of the standard drive gear and the hoist for initial installation and removal of the hoist or drive gear for repair purposes. However, where the driven apparatus is of a type requiring a highly secure connection, such as in a hoist, standard connectors that are presently available and suitable for making the connection may not be entirely satisfactory.